In the design of architectural structures, it is relatively common to construct a large structure in independent segments, adjacent but spaced from each other, to allow for a degree of relative movement between the sections. Such movement may be caused by expansion and extraction factors, for example, seismic activity or the like. Typically, a suitable cover for seal is provided to span the joint between the two structures while allowing for the designed degree of relative motion. For certain types of installations, for example floors, it is advantageous to employ an elastomeric sealing element which extends between the adjacent structures. The elastomeric element is bonded at opposite sides to the structures and, in the case of floor sections, provides a relatively smooth continuation of the floor surface suitable for pedestrian traffic and light vehicles. The elastomeric element is allowed to stretch, retract, twist and distort, as necessary to accommodate the expected relative movements of the adjacent structures. One known form of such elastomeric joint seals is reflected in U.S. Pat. No. 3,849,958.
Particularly where the joint seal spans a substantial open space between the structures and/or a substantial vertical load may be expected (e.g., from light wheeled vehicles), the elastomeric sealing element is provided with a rigid support member underlying the elastomeric sealing element and supporting the same vertically while allowing the necessary sliding, stretching, retracting, twisting motions that the joint seal is required to accommodate.
Historically, architectural joints sealed with elastomeric sealing elements of the type described above have been subject to failure to a greater degree than desired. Such failures can be either cohesive failure or adhesive failure. For example, if the stresses applied at the adhesive interface exceed the adhesion bond, an adhesion failure will occur. To reduce the likelihood of adhesion failure, the elastomeric element can be configured to have a reduced cross section in the center, as reflected for example in the beforementioned U.S. Pat. No. 3,849,958. However, while this design can reduce the potential for adhesion failure, the likelihood of a cohesion failure is increased, so that one problem is traded off for another. Moreover, the seal is weakest at the center, where the vertical load stress are greatest.
Pursuant to the present invention, a novel and improved configuration of elastomeric seal and supporting element is provided, in which the bottom configuration of the elastomeric sealing element, and the conforming upper surface configuration of the underlying rigid support, is of a somewhat sinusoidal cross sectional configuration with the elastomeric seal having a section of greater thickness in the central regions. The arrangement of the invention provides for a plurality of regions, across the width of the elastomeric sealing element but spaced from the central portions thereof, in which widthwise elongation of the sealing element is facilitated. The arrangement is such that the stress level at the adhesive bond interface is minimized, while the cohesive stress of the elongation is effectively distributed, minimizing the potential for either adhesive or cohesive failure.
In an optimum form of the invention, a rigid supporting plate is provided with a concave central contour, merging with convex contours on either side thereof. A conforming elastomeric seal, typically formed by being poured in place over the supporting plate, thus is provided with a downwardly convex portion of increased thickness in its center, and downwardly concave portions of reduced thickness on either side thereof. Multiple advantages flow from this configuration, as will appear.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawing.